Investigating the appropriate adenosine deaminase cutoff value for the diagnosis of tuberculous pleural effusion in a country with decreasing TB burden

Abstract

As the burden of tuberculosis (TB) in South Korea decreases while that of malignancy increases with an aging society, the composition of etiology for pleural effusion is changing. The aim of this study was to investigate the diagnostic value of adenosine deaminase (ADA) for diagnosis of tuberculous pleural effusion (TPE) in this circumstance. Medical records of patients who underwent medical thoracoscopy from May 2015 to September 2020 in Incheon St. Mary Hospital, Korea were retrospectively reviewed. TPE was diagnosed if one of the following criteria was met: (1) granuloma in pleura, (2) positive TB polymerase chain reaction or culture in pleural fluid or tissue with non-specific pathologic findings in pleura, or (3) bacteriologically confirmed pulmonary TB with non-specific pathologic findings in pleura. A total of 292 patients, including 156 with malignant pleural effusion (MPE), 52 with TPE, and 84 with other benign effusion, were analyzed. Among 206 patients with lymphocyte dominant pleural effusion, the area under receiver characteristic curve of ADA for diagnosis of TPE was 0.971. The sensitivity and specificity of a current cutoff value of 40 IU/L were 1.00 and 0.61, respectively, whereas those of a raised cutoff value of 70 IU/L were 0.93 and 0.93, respectively. Among 54 patients with ADA levels of 40–70 IU/L, 30 (55.6%) patients were diagnosed as MPE, 21 (38.9%) as other benign effusion, and only 3 (5.6%) as TPE. Caution is needed in clinical diagnosis of TPE with current ADA cutoff value in countries with decreasing TB incidence, due to many false positive cases.

ADA as main biochemical marker in patients with tuberculous effusion

“…Numerous studies have been conducted on different populations, such as Spanish, Chinese, Brazilian, but the results agree that the sensitivity and specificity for TP are over 90% [21] .…”

“…In this way, faster diagnostics will be enabled without the application of more invasive diagnostic methods, as well as targeted and effective treatment. Although ADA is not the gold standard test for the diagnosis of TPE, it is recommended as a ‘rule out’ test in countries with a low prevalence of TB and »rule- in« test in countries with a high prevalence of TB [21] .…”

Case 17: A 62-Year-Old Man With Dyspnea and Chest Discomfort for 1 Month

“…The cutoff value for ADA is typically set at 70 U/L. 4 If the ADA level is above 70, it’s considered “probable TB,” and empiric anti-TB treatment may be considered. If the ADA level falls between 40 and 70, further evaluation is needed, considering the patient’s medical history, clinical presentation, and potential alternative diagnoses.…”

Tuberculosis Pulmonar Y Extrapulmonar en Niños

“…La ADA > 40 U/L es un indicador sensible para el diagnóstico de tuberculosis, pero su especificidad varía en torno a la incidencia (7), debido a la posibilidad de encontrar falsos positivos (9). El estudio bacteriológico del líquido pleural es generalmente negativo.…”